(使用树结构支持并查集8.4.1)UVA 10608 FRIENDS(查看一个集合中有多少个元素)

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int maxn = 30010;

int father[maxn],c[maxn];

int find(int x){
	if(father[x] == x){
		return x;
	}

	return father[x] = find(father[x]);
}

void join(int a, int b){
	a = find(a);
	b = find(b);

	if(a != b){
		father[a] = b;
	}
}
int main(){
	int t;
	scanf("%d",&t);
	while(t--){
		int n,m;
		scanf("%d%d",&n,&m);

		int i;
		for(i = 1 ; i <= n ; ++i){
			father[i] = i;
			c[i] = 0;
		}

		for(i = 1 ; i <= m ; ++i){
			int a,b;
			scanf("%d%d",&a,&b);

			join(a,b);
		}

		for(i = 1 ; i <= n ; ++i){
			int x = find(i);
			c[x]++;
		}

		int maxm = 0;
		for(i = 1 ; i <= n ; ++i){
			if(maxm < c[find(i)]){
				maxm = c[find(i)];
			}
		}

		printf("%d\n",maxm);
	}

	return 0;
}